1. Field
The exemplary embodiments generally relate to storage and retrieval systems and, more particularly, to automated storage and retrieval systems.
2. Brief Description of Related Developments
Many scientific and medical organizations, including industrial concerns, regulatory agencies, research laboratories, and academic institutions, have the need for secure storage of very large numbers, e.g., millions of samples and specimens. Such fields include pharmaceutical, biotechnology, laboratory diagnostics, genomics, biospecimen, forensic, agrichemical and specialty chemical. Depending on the application, the sample sizes can vary from tens of microliters to several drams, which are stored in small, sealed plastic tubes, vials or multiwell plates. The individual sample containers are retained in a rack that allows individual samples to be inserted or removed without removing an entire rack, or the sample group holder that holds one or more racks, from the system. To extend the useful lifetime of the samples, they are stored in a controlled environment of low temperature (typically −20° to −80° C. or lower), low humidity, and inert gas (nitrogen), and are subjected to as little environmental variation as possible. In order to handle very large numbers of samples in the most efficient manner, a number of considerations must be made to enhance the system's flexibility and adaptability for different applications.
An important component of many such storage systems is a robotic system, e.g., a sample group holder conveyor, for removing and replacing the racks and sample group holders from the storage compartment with minimal impact to the low temperature environment. The sample group holder conveyor delivers sample group holders or racks with selected samples to a controlled environment that is not as cold as the storage compartment, but is at some intermediate temperature between the low or ultra-low temperature of the storage compartment and the laboratory environment to prevent the samples from thawing. This controlled temperature area into which the sample vials are delivered may also be maintained in an inert atmosphere and low humidity environment. Another robotic system that works in cooperation with the sample group holder conveyor is the tube picker, sometimes referred to as the “cherry picker”, which allows individual tubes to be extracted from the sample group holder or rack that was retrieved from the storage compartment and placed into a separate sample group holder or rack for processing or analysis. An exemplary vial picker is described in U.S. Patent Publication No. US 2008/0044263, which is incorporated herein by reference in its entirety.
Briefly, the storage system controller, which also controls the sample group holder conveyor and tube picker operation, maintains a database of information about each sample including the location (e.g., shelf or carousel) at which it is stored within the storage compartment and its location within its sample group holder and rack. Once the sample group holder has been removed from the storage compartment and placed on the “pick table”, the tube picker moves within an x-y plane to pre-selected positions within the sample group holder that holds the samples to be extracted, which can be referred to as the “source sample group holder”. The tube picker includes a pusher mechanism, which lifts the sample containers up and out of the sample group holder, and a pick head, which has one or more cavities for receiving the sample containers that are lifted by the pusher mechanism. The pusher mechanism moves independently from the moveable pick head, allowing the pick head to receive multiple tubes from different locations of a sample group holder. The pick head is then moved to a destination over a destination sample group holder and the ejector mechanism is actuated, placing all tubes in one motion.
The small sizes and close packing of the tubes in the sample group holders means that considerable precision is required when picking the tubes from the sample group holders. The ability to precisely locate each selected tube becomes complicated due to, for example, the thermal effects on the sample group holder material. Specifically, the sample group holders can experience changes in length on the order of several millimeters, which makes it difficult for the picker to find and select the tube if it is a few millimeters away from where it is expected to be.